Track circuit apparatus



Jan. 7, w STQU'F ETAL 2,227,675

TRACK CIRCUIT AiPARATUS Filed Nov. 18, 1939 14 1 ,P l 5 10 3 B c 3/9INVENTOR5 lUaZzerL Siam and THEIR ATTORNEY Patented Jan. 7, 1941 UNITEDSTATES PATENT OFFICE TRACK CIRCUIT APPARATUS Walter L. Stout, PennTownship,

Allegheny County, and Arba G. Williamson, Carnegie, Pa., assignors toThe Union Switch & Signal Company, Swissvale, Pa., a corporation ofPennsyl- Vania Application November 18, 1939, Serial No. 305,158

5 Claims.

Our invention relates to track circuit apparatus and more particularlyto apparatus of this type having improved operating characteristics.

One object of apparatus embodying our invention is to provide a trackcircuit in which the track relay combination operates with increasedshunting sensitivity and a quicker and more positive release. Otherobjects and advantages will become clear from the description whichfollows.

We shall describe two forms of apparatus embodying our invention, andshall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing oneform of track circuit apparatus embodying our invention. Fig. 2 is adiagrammatic view showing a modified form of the track relay combinationshown in Fig. 1, also embodying our invention.

Similar reference characters refer to similar parts in each of the twoviews.

In railway signaling track circuits, it is desirable to maintain theupward pull on a track relay armature at a suitably low value when thetrack section is unoccupied so that when a train enters the section,sensitive release of the track relay will be obtained. One way in whichthis result can be accomplished is by means of the wellknownprimary-secondary relay combination 30 wherein a separate secondaryrelay is used to decrease the energization of the primary relayfollowing pick-up, so as to render the combination sensitive to thepresence of a train shunt. Our invention combines the functions of apri- 3 mary-secondary relay in one structure which is capable ofproviding certain additional advantages such as quicker and morepositive release of the track relay armature when a train enters thesection, and a more positive pick-up when 40 the section becomesunoccupied.

Referring to Fig. 1 of the drawing, the reference characters I and ladesignate the two rails of a section of track which is insulated fromadjoining sections by means of the usual insulated rail joints 2.Located at one end of the section is a suitable source of current, hereshown as a battery 3, which is connected across the rails through anadjustable current limiting resistor 4. Connected across the rails atthe other end of the section is a track relay. combination designatedgenerally by the reference character A. This relay combination comprisesa pair of magnet structures B and C with which the armature 5 cooperatesto provide the improved operation to which our invention is directed.The armature 5 is pivoted at 6 and operates the usual signal controllingcontacts (not shown) and also the back contact 'I--8. Suitablenon-magnetizable core pins limit the movement of the armature whenenergized. The contact 'l-8 is so adjusted that it will not open untilthe armature has almost reached its fully picked-up position.

The main magnet B of the relay A is provided witha pair of operatingcoils 9 and I normally connected in series with the magnetizing coils Hand I2 of the auxiliary magnet C. The coils I l and |2should beconnected in a direction such as to aid the flux which is established inthe armature by coils 9 and I0. Magnet C may also be provided with ashort-circuited winding ii), if desired, for a purpose which will bedescribed hereinafter. The windings, air gaps, and core structures ofthe magnets Band C are so designed and proportioned as to provide justsufiicient holding energy to maintain armature picked up under the wetballast condition but to insure pickup of the armature following theexit of a train under this same ballast condition.

If desired, the magnet B may be provided with a restrictedcore portionsuch as that indicated at IS. The sectional area of this restrictedportion should be such as to cause this portion of the core to becomesubstantially saturated at a flux density slightly above that normallyrequired to pick up the relay armature. In this manner, when the ballastdries out and the voltage at the relay terminals increases, the downwardpull of the magnet C will increase in greater proportion than the upwardpull of magnet B. Accordingly, the track relay combination will providea certainamount of compensation for track ballast resistance changes byvirtue of the change in the flux division between the magnets B and Cwhich is broughtabout by the restricted core portion J6. An additionaladvantage in providing magnet B with a restricted section is that underdry ballast conditions the flux in magnet B will tend to die away morequickly than would be the case if the flux were permitted to build up toa high value. Therefore, a train shunt effective at such a time willproduce a slightly quicker release of the armature.

The operation of the apparatus will be best understood from aconsideration of what happens when a train enters and leaves the tracksection.

Normally, when the section is unoccupied, the armature will be in thepicked-up position in which it is shown, Under this condition, the

back contact '!8 will be open so that the resistance of coils l l and [2will be effective to cut down the current in the operating windings 9and ID to its holding value. Also, there will be a downward pullexercised on the armature by the auxiliary magnet due to the currentflowing in windings H and I2. This pull will, of course, be insufficientto overcome the attraction established by the operating magnet B, sothat the armature will normally remain in its picked-up position.

When a train entersthe section, the shunt provided by the train willdecrease the current in coils 9 and I sufficiently to cause the armatureto release. After the armature has moved part way, it will close backcontact 'I8, thus short-.circuiting the windings II and [2. The snubbingeffect of these windings closed on themselves (aided by the snubbingeffect of ferrule winding l3, if used) will prevent a too rapid changeof flux in the core of magnet C so that this magnet will continue toexert its downward pull to aid full release of the armature. Theresistance of windings H and I2 will thus be eliminated from the circuitof coils 9 and lil so that an increased current will flow in thesecoils, but since the armature air gap is now relatively large, thiscurrent will not be sufficient to pick up the armature until the trainvacates the section. In practice, the shunt for windings H and I2 willpreferably pass through a suitable contact finger on the armature,rather than the armature itself, but is shown as passing through thearmature in order to simplify the disclosure. Subsequent pick-up of thearmature is aided not only because the current in windings 9 and I0 isincreased, but also because the downward or opposing pull of magnet Cbecomes negligible a short time after the back contact 'l-B becomesclosed.

As soon as the train leaves the section, the train axle shunt will beremoved from across the operating coils 9 and so that the full pick-upenergization will be effective in magnet B. Accordingly, the armaturewill quickly pick up and in so doing will open contact 1--8 near the endof its stroke, thus restoring the apparatus to its normal condition inwhich it is illustrated.

The short-circuited or ferrule winding l3 may or may not be used, aspreferred, but when used, this winding performs a useful function inthat it accentuates the beneficial effect of the .auxiliary magnet C.When a train enters the section, the flux in magnet B will collapse morequickly than in magnet C because the flux in the latter magnet will bemaintained for .a short interval of time through the action of theferrule l 3, even before contact '!-8 becomes closed. Accordingly, thedownward pull of magnet C will decrease more slowly than the upward pullof magnet B and will persist for a longer time, thus providing a quickerand more positive release of the armature. Conversely, when the trainleaves the section, the ferrule 13 will prevent the flux in magnet Cfrom building up as rapidly as in magnet B, so that the latter magnetwill have ample opportunity to pick up the armature before the opposingpull of magnet C becomes fully effective. During the time that contact1-8 is closed, the windings II and I2 act somewhat in the nature ofwinding 13, and for this reason the resistance of these windings shouldnot be too high. This resistance must, of course, be sulficient ascompared with that of windings 9 and H] to provide the necessary spreadbetween the pick-up and holding torque of the relay.

The ferrule l3 has an additional advantage in that it provides duringthe initial shunting interval a certain amount of compensation for trackballast resistance changes, (in addition to the compensation whichresults from the use of the restricted core portion l6) by preventingtoo great a decrease in shunting sensitivity when the ballast dries out.Under dry ballast conditions with the track unoccupied, the energizationof both magnets B and C will be relatively high due to the increasedtrack voltage then effective. When a train shunt is applied at such atime, the high initial energization in magnet C is actually helpfulbecause, in view of the unequal rate of decay of the fluxes in magnets Band C caused by the ferrule 13, (as well as the restricted section IS)the increased downward pull due to high. energization of magnet 0 tendsto offset to some degree the higher initial energization of magnet B.Accordingly, more uniform shunting sensitivity tends to be maintainedover a wider range of ballast resistance variation, due to the presenceof the ferrule winding l3.

Referring now to Fig. 2, the track relay combination of this figure isquite similar to that of Fig. 1, with the exception that the backcontact 1-8 as well as the short-circuit for windings H and [2 are botheliminated and the ferrule winding I3 is replaced by .a pair of ferrulewindings l4 and I5 for increased effect. The operation of the apparatusshown in Fig. 2 will be clear from the description of the apparatus ofFig. 1, and particularly those portions which deal with the effect ofthe restricted core portion 16 and the effect of the ferrule winding I3.Since the current in the operating magnet B is not decreased afterpick-up of the armature in Fig. 2, the improvement in shuntingsensitivity is due mainly to the slower rate of decay of the flux inmagnet C, whereby a quicker and greater downward pull is effective forreleasing the armature when a train enters the section. Similarly, aquicker and more effective upward pull for picking up the armature bymeans of magnet B is present when a train leaves the section, since theflux in magnet C will lag appreciably behind the flux in magnet B. Twoferrules I l and [5 are pref erably used and are placed in closeproximity to the coils H and I2, respectively, in order that retardationof the flux change in magnet C may be as great as possible. Obviously,.a single ferrule, as in Fig. 1, may be used in the apparatus of Fig. 2.Also, in Fig. 1, if it is desired to in crease the ferrule effect, twoferrules placed as in Fig. 2 may be employed.

Although we have shown the two magnets B and C located one over theother with the armature in between, this has been done mainly forconvenience in illustration. Obviously, the two magnets may be placedside by side, with the armature pivoted between them so that opposingarmature torques are produced thereby. It will be understood, therefore,that magnet C may be positioned in many other obvious ways with respectto the magnet B, provided that it produces an opposing torque on thearmature, without altering the inventive concept underlying ourinvention.

Although we have herein shown and described only two forms of trackcircuit apparatus embodying our invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of ourinvention.

Having thus described our invention, what we claim is:

1. In combination with a section of railway track and a source ofcurrent connected across the rails of said section, a track relay havingtwo magnetic circuits so arranged with respect to the armature that oneaids pick-up of the armature and the other opposes pick-up thereof, anoperating winding for said aiding magnetic circuit connected across therails of said section and effective for causing said armature to pick upwhen said section is unoccupied, an energizing winding for said opposingmagnetic circuit connected in series with said operating winding andefiective to aid the release of said armature when the section becomesoccupied, and means for v causing said aiding magnetic circuit to becomemagnetic circuits so arranged with respect to the armature that one aidspick-up of the armature and the other opposes pick-up thereof, anoperating winding for said aiding magnetic circuit connected across therails of said section and effective for causing said armature to pick upwhen said section is unoccupied, an energizing winding for said opposingmagnetic circuit connected in series with said operating winding andeifectve to aid therelease of said armature when the section becomesoccupied, and a core portion of restricted sectional area in said aidingmagnetic circuit for causing substantial saturation thereof when thetrack ballast of said section dries out whereby the relative pull ofsaid opposing magnetic circuit will be increased to thereby providepartial compensation for ballast resistance variations.

3. In combination with a section of railway track and a source ofcurrent connected across the rails of said section, a track relay havingtwo magnetic circuits so arranged with respect to the armature that oneaids pick-up of the armature and the other opposes pick-up thereof, anoperating winding for said aiding magnetic circuit connected across therails of said section and effective for causing said armature to pick upwhen said section is unoccupied, an energizing winding for said opposingmagnetic circuit connected in series with said operating winding andeffective to aid the release of said armature when the section becomesoccupied, means associated with said opposing magnetic circuit forretarding a rapid flux change therein to aid quick release of saidarmature when the section becomes occupied and to aid quick pick-up ofsaid armature when said section becomes unoccupied, and means forcausing said aiding magnetic circuit to become substantially saturatedwhen the track ballast of said section dries out to thereby increase therelative pull of said opposing magnetic circuit and partly compensatefor ballast resistance variations.

4. In combination with a section of railway track and a source ofcurrent connected across the rails of said section, a track relay havingtwo magnetic circuits so arranged with respect to the armature that oneaids pick-up of the armature and the other opposes pick-up thereof, anoperating winding for said aiding magnetic circuit energized from saidsource over the rails of said section, an energizing winding for saidopposing magnetic circuit also receiving current from said source oversaid rails and efiective to aid the release of said armature when thesection becomes occupied, and means for causing said aiding magneticcircuit to become substantially saturated when the track ballast of saidsection dries out to thereby increase the relative pull of said opposingmagnetic circuit and partly compensate for ballast resistancevariations.

5. A track relay for improving the shunting sensitivity of a trackcircuit comprising, in combination, two magnetic circuits each includingthe armature of said track relay as the common portion thereof, anenergizing winding for each of said magnetic circuits, one of saidmagnetic circuits being efiective to pick up said armature when itsassociated winding is energized and the other of said magnetic circuitsbeing effective to establish an opposing torque on said armature whenits associated winding is energized for at times aiding the release ofsaid armature, means for passing the same energizing current throughboth of said windings, and means for causing said one magnetic circuitto become substantially saturated above the pick-up value of saidarmature to thereby increase the relative pull of said other magneticcircuit and partly compensate for the effect of excess current in thewindings of said track relay.

WALTER L. STOUT. ARBA G. WILLIAMSON.

